The first egg box was invented in Canada in 1911. It was a 12-egg box (patent sketch, and another by the same inventor in 1927). It is probable that this boxing has given a popularity to "dozen" eggs.
However, "dozen" had been already an important trade number. Maybe it was already in use for selling eggs.

The duodecimal system is a very ancient system that has survived in certain settings, such as imperial measures (12 inches to a foot), time telling, and goods like eggs (6 or 12), beer/wine (6, 12, 24), baked goods (12+1 is a baker's dozen) etc. The dozen is a natural choice due to its many factors.

The duodecimal system is a very ancient system that has survived in certain settings, such as imperial measures (12 inches to a foot), time telling, and goods like eggs (6 or 12), beer/wine (6, 12, 24), baked goods (12+1 is a baker's dozen) etc. The dozen is a natural choice due to its many factors.

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Not to mention monetary systems too - a number of European systems were descended from the Roman libra-solidus-denarius system which continued in the UK until 1971 when Britain finally went decimal. In that system, there were 12 pennies (denari) to a shilling (solidus) (and then 20 shillings to a pound).

Curiously, most (or all?) languages that have a special word for “dozen” (as opposed to the number “twelve”) have borrowed this term either from French “douzaine” or from Italian “dozzina”. This includes forms like Arabic dazzīna, Turkish düzine, Russian дюжина, and (from Russian) Persian dojīn.

Curiously, most (or all?) languages that have a special word for “dozen” (as opposed to the number “twelve”) have borrowed this term either from French “douzaine” or from Italian “dozzina”. This includes forms like Arabic dazzīna, Turkish düzine, Russian дюжина, and (from Russian) Persian dojīn.

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Definitely not all. The Hebrew word for dozen is treysar (תריסר). It comes from roots that mean "two" and "ten."

Curiously, most (or all?) languages that have a special word for “dozen” (as opposed to the number “twelve”) have borrowed this term either from French “douzaine” or from Italian “dozzina”. This includes forms like Arabic dazzīna, Turkish düzine, Russian дюжина, and (from Russian) Persian dojīn.

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This is very interesting indeed!

Egmont, there is no special word for "dozen" in Biblical Hebrew, but we use "תרי-עשר"/"תריסר" (tre-assar/tressar) which is the Aramaic "twelve", if we explicitly want to say "dozen".

The duodecimal system is a very ancient system that has survived in certain settings, such as imperial measures (12 inches to a foot), time telling, and goods like eggs (6 or 12), beer/wine (6, 12, 24), baked goods (12+1 is a baker's dozen) etc. The dozen is a natural choice due to its many factors.

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The word dozen and all the versions in other IE langauges in Europe comes from Latin duodecimus, later tranasformed into French dozaine. Hence: docena, dozen, dusin, dutzend, dusin, dussin, dozijn, dozzina, tuzet, tuzin, дюжина. Only Greek breaks out of the range with δωδεκάδα, while the Finno-Ugrian langauges have tucet (H), tosin (Est) and tusina (Fin).

The word dozen and all the versions in other IE langauges in Europe comes from Latin duodecimus,

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Yes, but not DIRECTLY from Latin, but from Italian dozzina, which in turn is from French douzaine. "dozen" is basically a commercial term ("set of twelve goods") which proliferated at the time when Venice and Genoa controlled much of international trade.

The word dozen and all the versions in other IE langauges in Europe comes from Latin duodecimus, later tranasformed into French dozaine.

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French douze (twelve) is derived from the cardinal number duodecim. The ordinal number duodecim-us/-a/-um produced French douzième. The -n in dozen needs to be explained differently. In French, -aine is a productive suffix to produce collective nouns. For a group of one hundred persons you say une centaine de personnes or for a eight pages long passage in a book you say une huitaine de pages. In modern French this construct une xxx-aine de is often used to expresses about xxx.

EDIT: Crossed with fdb's post.
@fdb: Do we really need Italian to explain douzaine? The suffix -aine can directly be traced back to the Latin adjective -ān-us/-a/-um. Also the function of the suffix to produce collective nouns exists in other French words derived from this suffix, e.g. monatānus > ... > montagne. Dozzina seem to be cognate to douzaine and not its etymon.

French douze (twelve) is derived from the cardinal number duodecim. The ordinal number duodecim-us/-a/-um produced French douzième. The -n in dozen needs to be explained differently. In French, -aine is a productive suffix to produce collective nouns. For a group of one hundred persons you say une centaine de personnes or for a eight pages long passage in a book you say une huitaine de pages. In modern French this construct une xxx-aine de is often used to expresses about xxx.

EDIT: Crossed with fdb's post.
@fdb: Do we really need Italian to explain douzaine? The suffix -aine can directly be traced back to the Latin adjective -ān-us/-a/-um. Also the function of the suffix to produce collective nouns exists in other French words derived from this suffix, e.g. monatānus > ... > montagne. Dozzina seem to be cognate to douzaine and not its etymon.

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Of course, douze comes from dudecim not dudecimus, sorry, too fast typing.
I did'nt say that douzaine comes directly from Latin, it was just a short wat of expressing it.
Which language spread the word all over Europe: French or Italian?

Please read again what I wrote. douzaine is a genuine French formation. dozzina is borrowed, or rather restructured, from French, with the Italian suffix -ina. The Arabic, Turkish, Russian etc. forms are borrowed from Italian in the age of Venetian/Genoese mercantile supremacy. Hindi/Urdu darjan is borrowed from English.

Hungarian tucat (from tutsat, the Bavarian-Austrian version of the German dutzend)

The formation of the proper word in Romance languages is quite regular, e.g. in Spanish we have also decena (amount of 10), veintena (20), treintena (30) centena (100) ... So the word docena and its variants in other Romance languages do not a priori presuppose the pre-existence of a duodecimal system of counting.

Neigther 12 months in a year nor twice 12 hours in a day are due to a duodecimal system. The importance of 12 in astronomy is given probably by the 12 lunar cycles in a year, independently on the counting system. By the way, the Roman calendar had originally only 10 months (January and February were added later).

Of course, 12 as unit may be a heritage or borrowing from people that had a duodecimal system, but maybe they were other reasons for counting eggs in dozens ...

P.S. Sorry, I have not noticed the previous 3 posts while writing this post ...

Does it mean that the Germanic languages borrowed directly from French?

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With respect to English, I would say yes. In the case of German, I am simply not sure. The word entered German only around 1500, so it may have arrived via Italian and French concurrently. The spelling with <tz> corresponds in pronunciation to the Italian <zz> but there are also historical spellings with <ou> and only one <z> that suggest French influence.

The duodecimal system coexisted with the decimal system in a long time, especially in the commercial use. Regarding eggs, they have been sold in centuries not only by dozens but also by sixty-units.

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I understand, but we have to distinguish the proper duodecimal number system (where the base is 12 and not 10) from the usage of 12 as unit for certain purposes. Languages that use duodecimal systems are very uncommon (though probably not inexistent). On the other hand, for example, the historical presence of the vigesimal number system is attested also in Europe (probably of Vasconic origin). As consequence, we have e.g. quatre vingt instead of huitante (octante) in standard French (i.e. the base for expressing 80 is 20 and not 10).

All I wanted to say is that it is not necessary to presuppose the existence of a language that has/had a duocecimal number system to explain the practical usage of dozens. Various units were used in the past for different purposes, regardless of the number system (e.g. 1 yard = 3 feet, 1 perch = 5.5 yards, 1 acre = 40x4 perches etc...).

French douze (twelve) is derived from the cardinal number duodecim. The ordinal number duodecim-us/-a/-um produced French douzième.

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The suffix -ième comes from Latin ordinal forms, but douzième must be a derivation within French, douze + -ième. You can't go directly from duodĕcĭmum to douzième by regular sound change (intervocalic [d] should not become an affricate).

The suffix -aine can directly be traced back to the Latin adjective -ān-us/-a/-um. Also the function of the suffix to produce collective nouns exists in other French words derived from this suffix, e.g. monatānus > ... > montagne.

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Montagne is from montānea, and I don't think this -ān- necessarily has any collective meaning. It's just a relational suffix. As for -ain(e), the origin seems in fact to be the Latin distributive/multiplicative suffix -ēni, not -ānum. (But again, douzaine doesn't derive directly from duodēni.) The modern spelling indicates that at some point it probably was assimilated to the relational -ain(e) < -ānum.

Indeed. The correct Aramaic spelling is of course תריעסר (Syriac ܬܪܥܣܪ) and the Middle Aramaic pronunciation is /treʻsar/ with ע.

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It must be different among Aramaic dialects. In Jewish "Middle" Aramaic both תריסר and תרי עשר appear, I guess that the former is a general eastern Aramaic (Babylonian) form and the latter is influenced by Hebrew, where both ע (`ayin) and ש (sin) survived much later.

Back to the eggs - in Israel they are usually sold in boxes of 12 or 36, yet I don't think there's a word for that.

The duodecimal system is a very ancient system that has survived in certain settings, such as imperial measures (12 inches to a foot), time telling, and goods like eggs (6 or 12), beer/wine (6, 12, 24), baked goods (12+1 is a baker's dozen) etc. The dozen is a natural choice due to its many factors.

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I don't know if you made a pun on purpose, but I think the fact that divides evenly by 2, 3, 4, and 6 makes it convenient. In particular, a half dozen, a quarter dozen, and a third of a dozen are all whole numbers, so a dozen is easily broken without breaking the eggs.

I have some more ideas on why the numbers 6 and 12 are practical when it comes to eggs:
1) Whe you collect and carry eggs with bare hands, you can easily hold 3 in each hand by securing one egg between every two of the long fingers and still having the thumb free to scratch your nose or for other uses.
2) Primitive implements to hold and carry eggs could easily be made by dividing a round holder in six equal parts, like this. http://thumbs1.ebaystatic.com/d/l225/m/mQqO7xoeGW15YcduIDvluYQ.jpg
But dividing a circle in five or seven is complicated and leaves lots of unusable space.